Mayor Bloomberg on NBC today, announcing a crackdown on seniority-based layoffs and a new tenure policy.

In his first major education policy announcement for the new school year, Mayor Michael Bloomberg this morning vowed a renewed attack on seniority laws that protect veteran teachers and a change in how teachers are awarded tenure.

He made the remarks on NBC, which is dedicating this week to school reporting in a project called “Education Nation.”

The attack on seniority laws came as city officials made a dire budget prediction for next year, saying that they will likely have to lay off public school teachers as federal stimulus funding runs out. Under the current state law, teachers with the least seniority would be the first to lose their jobs — a policy known as “last in, first out.” The mayor and Chancellor Joel Klein oppose this policy, but their effort to change the law, which the teachers union does support, went nowhere last year.

Today, the mayor said he would try dismantling the policy again before the city confronts an expected $700 million budget hole and possible layoffs next year.

“It’s time for us to end the ‘last-in, first out’ layoff policy that puts children at risk here in New York — and across our wonderful country,” Bloomberg said on NBC. “How could anyone argue that this is good for children? The law is nothing more than special interest politics, and we’re going to get rid of it before it hurts our kids,” he added.

Teachers union officials immediately squashed any possibility that they might partner with the mayor.

“The seniority layoff process is part of state law and a critical guarantee against discrimination,” United Federation of Teachers president Michael Mulgrew said in an e-mailed statement. “If the Mayor wants to change seniority, he will need to talk to the Legislature,” Mulgrew said. “Given that body’s lack of enthusiasm for many of the Mayor’s plans — like congestion pricing — we expect an appropriate amount of skepticism.”

Assemblyman Jonathan Bing, who introduced the bill to end seniority-based layoffs last year, is running for reelection this November and is likely to hold onto his seat. He has said that he will continue to push for the law’s repeal if he is re-elected.

Bloomberg also announced plans to change how teachers are given tenure.

Last year, Bloomberg had announced a first major shift in the tenure-granting process. For the first time, students’ test scores became a formal factor, as the city ranked teachers eligible for tenure by their value-added scores, a complex and sometimes-unstable measurement of effectiveness. Principals were then advised to deny tenure to the lowest-scoring teachers, though they could override the city’s recommendations.

This year, Bloomberg said the city will add more information to the decision process by way of a new teacher evaluation system passed by the state legislature this year. The evaluation system uses a combination of information, including principal evaluations and value-added scores, to rank teachers in one of four categories — highly effective, effective, developing, and ineffective.

All 6,300 teachers who are eligible for tenure this year will be placed in one of these categories. Principals will be instructed to deny tenure to “developing” and “ineffective” teachers, said DOE spokeswoman Ann Forte.

Mulgrew swiped at this set of comments, too, taking issue with Bloomberg’s description of tenure as “automatic.” But the teachers union president said that teachers would likely prefer the new evaluation system — which was passed with the union’s support — as a more “objective” alternative to the current model.

Tacked onto the mayor’s announcement was also news that the city is partnering with IBM and the City University of New York to open a new school. Serving students in grade 9-14, the school would graduate students with associates degrees in computer science and the promise of a job at IBM.